docs: add custom checkpointer implementation guide with delta channel support#4163
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Sydney Runkle (sydney-runkle) wants to merge 1 commit into
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docs: add custom checkpointer implementation guide with delta channel support#4163Sydney Runkle (sydney-runkle) wants to merge 1 commit into
Sydney Runkle (sydney-runkle) wants to merge 1 commit into
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… support Adds src/oss/python/integrations/checkpointers/build-custom.mdx covering the full BaseCheckpointSaver contract, row key design, serialization requirements, and a dedicated section on DeltaChannel support (what get_delta_channel_history does, the default walk, a performance override pattern, and pruning/copy-thread caveats). Updates the checkpointers integrations index and langsmith/custom-checkpointer pages to link to the new guide. Adds the page to docs.json navigation as a sub-group under Checkpointers.
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Thanks for opening a docs PR, Sydney Runkle (@sydney-runkle)! When it's ready for review, please add the relevant reviewers:
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Summary
src/oss/python/integrations/checkpointers/build-custom.mdx— a new implementation guide covering the fullBaseCheckpointSavercontract, row key / index design, serialization requirements, and a dedicated delta channel support sectionget_delta_channel_historydefault walk (and whyget_tuple(by-id)must be correct), a performance-override pattern, and pruning / copy-thread caveatscheckpointers/index.mdxandlangsmith/custom-checkpointer.mdxto link to the new guidedocs.jsonto a sub-group with both the index and the new build pageMotivation
Surfaced from a customer support case: a custom Bigtable checkpointer was silently producing empty delta channel state. Root cause was a pre-existing
get_tuple(by-id)bug that delta channels promoted from "only hit during time travel" to "hit on every graph load." No docs existed explaining what theget_tuplespecific-id path is required for, or what delta channels need from a checkpointer.Test plan
langgraph.checkpoint.base.BaseCheckpointSaver/oss/python/integrations/checkpointers/build-custom,/langsmith/custom-checkpointer, and/oss/langgraph/persistenceresolve